1. Field of the Invention
The present invention relates to an electromagnetic wave shielding laminate having a plurality of layers laminated on a substrate and a display device provided with such an electromagnetic wave shielding laminate.
2. Discussion of Background
Electromagnetic waves are emitted from a luminescent screen of a plasma display panel (PDP). Such electromagnetic waves are influential over electronic equipment located nearby to cause malfunction thereof. Therefore, for the purpose of shielding such electromagnetic waves, it has heretofore been known to install on the front surface of the luminescent screen one having a transparent electroconductive film covered on a substrate of e.g. glass.
For example, a laminate wherein titanium oxide and a metal layer are alternately laminated, or a protecting plate for PDP coated with a multilayer conductive film, wherein an oxide layer containing, as the main component, zinc oxide (ZnO) containing at least one metal, and a metal layer containing silver (Ag) as the main component are alternately laminated in a total of (2n+1) layers (wherein n is a positive integer) from the substrate side, has been proposed (Patent Documents 1 and 2).
Such an electromagnetic wave shielding film is usually required to have a high visible light transmittance and a low resistivity. With an electromagnetic wave shielding film having an oxide layer and a metal layer alternately laminated, it is commonly known to increase the number of metal layers laminated or to make metal layers thick, in order to lower the resistivity.
Patent Document 1: WO98/13850
Patent Document 2: JP-A-2000-246831
In prior art disclosed in the above Patent Document 1, palladium is doped to a silver layer in order to improve the moisture resistance of silver. There has been a problem that the resistivity thereby increases. If the number of laminated metal layers is increased in order to lower the resistivity, there has been another problem that the visible transmittance will thereby decrease.
Whereas, in prior art disclosed in Patent Document 2, titanium oxide being a material having a high refractive index, is used as an oxide layer. If a material having a high refractive index like titanium oxide, is used, there will be a merit such that even when the number of laminated layers is increased, the decrease in transmittance will be small. However, the laminate having titanium oxide and silver alternately laminated, has had a problem that the moisture resistance is poor. By adding palladium to silver, the moisture resistance may be improved, but there has been a problem that the resistivity will increase by the addition of palladium.